Chairs that are used for a variety of purposes, such as office chairs, chairs for home use, vehicle chairs or seats etc. sometimes include a special lumbar support device to support the lumbar spine of the user. Usually this device is a softly rounded protrusion or cushion that is disposed on the front of the back support and a certain level above the seat. Below this protrusion, the person sitting on the seat may push in his pelvis until the protrusion bears against the lower back so that the lower back is in an ergonomically desirable, sway-backed or bow shaped position.
Although earlier known chairs (see, for example, U.S. Pat. No. 1,836,630) have an ergonomical shape that theoretically provide a good support for the lumbar spine, there is no guarantee that the user is really going to take advantage of the possibilities of the chair with regards to the entire potential of the back support to support the back in a physiologically optimal way. An optimal use requires that the user of the chair is required to intentionally push back the his bottom into the area below the lumbar support device. For various reasons, such as forgetfulness, stress, laziness or negligence, the user often does not push in the bottom against the part of the back support that is positioned below the sway back supporting protrusion. The result is that there is a gap between the bottom and the back support, so that the sway-back position of the back bone is mediocre. In other words, the body posture of the user becomes wrong and tiresome which can easily create back pain.
One object of the present invention is to solve the above-mentioned problems associated with the earlier known chairs as mentioned above and to create an improved chair. A fundamental purpose of the invention is thus to create a chair that ensures a complete support of the user's back against the lumbar support of the back support without requiring the user to intentionally push in the bottom against the lower part of the back support that is situated below the lumbar support device. Another object is to create a chair that permits a wide variety of user functions. More particularly, the required pushing in of the bottom may be accomplished automatically or with a motor force.
Yet another object is to create a chair that prevents the tendency of users that sit on the seat to slide forwardly along the seat of the chair. In other words, the construction of the chair is such that the person sitting on the chair maintains his bottom in contact with the lower part of the back support in a lasting reliable way.
WO-A-97/10735 describes a chair that has a seat and a back support that are generally movable towards or away from one another. The purpose of the movability between the seat and the back support is to achieve a pressure reduction on the user's bottom and lumbar spine that can be accomplished be forming a recess in the area between the rear edge of the cushion included in the seat and the back support that is disposed behind the seat. In this case, however, the seat is arranged to be locked into set positions after a the seat or the cushion have been moved to a desired position.
The known chair includes, therefore, no means for handling the three functions depending upon whether the user is sitting on the chair or is leaving the same, namely to hold the seat in the starting position, to activate a relative movement between the seat and back support when the user sits down on the seat, and to activate the return of the seat to the starting position when the user leaves the seat, as is stipulated in the present invention.
U.S. Pat. No. 5,244,252 discloses a vehicle seat that is movable between front and rear end positions. In this case, however, the seat is movable in a rock like manner along a bow shaped path which a central point situated above the seat. When the user sits down on the seat, the seat can move in a forward direction towards a front end position. In other words, this chair does not include means for moving the seat and the back support in a clear and controlled manner towards one another with the purpose of pushing the back of the user against the lumbar support device disposed behind thereof without requiring the user to have to take special, intentional steps therefor.
The chair of the present invention is comfortable and easy to adjust to the specific needs of the user. The chair also provides good support for the back of the user. The user of the chair may also move within the chair without losing the good support of the back of the user.